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THE SUBSPECIES OF THE MOUNTAIN CHICKADEE

BY

JOSEPH GRINNELL

UNIVERSITY OF CALIFORNIA PRESS
BERKELEY

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THE SUBSPECIES OF THE MOUNTAIN CHICKADEE

BY

JOSEPH GRINNELL

(Contribution From the Museum of Vertebrate Zoology of the University of California)

Fieldwork was carried on by the California Museum of Vertebrate Zoology during 1917 in the Inyo region of eastern California. In going over the collection of birds obtained, the attention of the writer was arrested by certain peculiarities evident in the Mountain Chickadees. Comparison with series from the Sierras showed the Inyo birds to be paler colored and longer tailed; and in order to appraise these differences in taxonomic terms it became necessary to assemble material representative of the entire range of the species, in so far as possible. The results of the study thus undertaken are presented herewith.

The material involved in the inquiry has amounted to 464 skins of the Mountain Chickadee, derived from the following sources other than the Museum of Vertebrate Zoology: United States National Museum, through Dr. Charles W. Richmond; United States Biological Survey, through Mr. Edward W. Nelson; and the private collections of Messrs. Edward R. Warren, Joseph and John W. Mailliard, G. Frean Morcom, Harry S. Swarth, and J. Grinnell.

As of general interest, and in the nature of an introduction to the systematic analysis to follow, it may be stated that Penthestes gambeli including its subspecies is throughout its range non-migratory, save as a few individuals in pairs or small companies occasionally descend in fall or early winter to lower levels closely adjacent to their mountain habitats. The range of the species roughly extends from and includes the Rocky Mountains to or nearly to the Pacific Coast, and from Alberta and British Columbia south nearly to the Mexican line--somewhat south of it in northern Lower California. Within this general area the Mountain Chickadee is by no means uniformly distributed. [506] Especially towards the south is its range very "spotty," the representations on detached mountain tops being wholly isolated. Two main areas of relatively continuous distribution are, however, perceivable--the Rocky Mountain area, and the Sierra Nevada area.

Fig. 1. Map showing distribution of the races of the
Mountain Chickadee in California.
Click on map to view larger version.

Close scrutiny of the series of specimens at hand well representing the entire Rocky Mountain area reveals no variation in phylogenetic characters from the northernmost to the southernmost stations. All show in apparently equal degree the long tail and cinnamon tinge of sides and back, these features together constituting the grounds for separate subspecific recognition of a Rocky Mountain form. On the other hand, the Sierra Nevadan center, with its own recognizable race, [507] of relatively short tail, proves to have two outlying divergent forms. These three forms are alike in their lack of any cinnamon tinge, this being replaced in two of them by a buffy tinge and in one form by leaden gray. The tail in one of the outlying forms is long, in the other short. The habitats concerned are, respectively, the desert mountains of the Inyo region of eastern California, and the coastal mountains of southern California. This differentiation within the Pacific district, particularly within the state of California, will be better understood in its geographic bearing by reference to the accompanying map (fig. 1).

The behavior of the tail of Penthestes gambeli--long in the Rocky Mountain district, short in the Pacific district (see figs. 2, 3)--is paralleled in the Penthestes atricapillus group of chickadees across the North American continent in about the latitude of the state of Washington. In the northern Rocky Mountains occurs the race P. a. septentrionalis, with long tail; in the Pacific Coast strip of Washington and Oregon occurs the race P. a. occidentalis, with, among other characters, relatively short tail. Other parallels are to be found in the genera Psaltriparus, Thryomanes and Pipilo.

Fig. 2. Tail of Penthestes gambeli gambeli (no. 27784, Mus. Vert. Zool.; ♂, full-grown juv.; Sierra Ancha, Gila Co., Arizona; June 26, 1917). × 1.00.

Fig. 3. Tail of Penthestes gambeli abbreviatus (no. 24059, Mus. Vert. Zool.; ♂, full-grown juv.; Yolla Bolly Mt., Tehama Co., California; August 5, 1913). × 1.00.

It is improbable that the fact of subspecific differentiation in Penthestes gambeli has been altogether overlooked previous to the present time. A premonition of the geographic variation now formally pointed out is to be found in the early writings of Baird (1858, p. 394), who remarked that "a specimen, apparently of this species [Parus montanus], from Medicine Bow creek [Wyoming], (5643,) though marked female, is larger than those from California, as shown by the measurements." Also, some of the differences in proportions in the subspecies now recognized are shown in the table of measurements given by Ridgway (1904, p. 409).

For a detailed description of the Mountain Chickadee as a species, the reader is referred to Ridgway (1904, p. 408).

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Type locality.--Santa Fé, New Mexico.

Diagnosis.--Among the four subspecies of Penthestes gambeli here recognized, color alone is sufficient for distinguishing P. gambeli gambeli. The flanks, sides of body and back in this form are pervaded with a distinct tinge of cinnamon--more exactly, the "pinkish buff" of Ridgway (1912, pl. 29). In addition, this race shows the greatest length of tail, and slenderest bill.

Measurements.--Average of 14 males: Wing, 70.5 mm.; tail, 70.2; exposed culmen, 8.6; depth of bill at base, 3.8. For extremes, see accompanying table.

Neither depth of bill nor culmen is a practical index to degree of slenderness of bill. No ordinary method of measurement will suffice to indicate the facts as they are perceived by the eye.

As will be seen by the dates in the tables, as a rule only unworn specimens have been selected for measurement.

Range.--The Rocky Mountain region of North. America, from eastern British Columbia and western Alberta south to western Texas, New Mexico and Arizona. Specimens examined, 72, from the following localities:

Type locality.--Panamint Mountains (northern part), 3 miles east of Jackass Spring, 6200 feet altitude, Inyo County, California. Type, male adult, no. 28782, Mus. Vert. Zool.; October 7, 1917; collected by J. Grinnell, orig. no. 4588.

Diagnosis.--The palest colored race of the four; sides, flanks and back, in unworn plumage, pervaded with pale buff--the "cartridge buff" of Ridgway (1912, pl. 30). Wear or fading, or both, removes most of this buff tone, so that the resulting effect, in spring and summer birds, is of an ashy tone of coloration, distinctly lighter than in any of the other three subspecies, in same stage. It seems probable that there is a paler tone to the underlying plumage parts and that this becomes revealed by loss of the superficial pigment-bearing portions through the gradual progress of feather abrasion. Inyoensis shows nearly as long a tail as does gambeli. Its bill is somewhat smaller.

[510] Measurements.--Average of 10 males: Wing, 71.1 mm.; tail, 69.3; exposed culmen, 8.1; depth of bill at base, 3.7. For extremes, see accompanying table.

Range.--The higher mountains of eastern California lying east and southeast of Owens Valley, from the vicinity of the Mono Craters and the White Mountains, in Mono County, south to the Panamint Mountains, in Inyo County. Specimens examined, 50, from the following localities, all in California:

Type locality.--Horse Creek, Siskiyou Mountains (near Seiad Valley P. O.), Siskiyou County, California. Type, male, no. 119 (orig. no., in coll. J. Grinnell); December 12, 1901; collected by Malcolm P. Anderson.

Diagnosis.--Tone of color on sides, flanks and back the same as in inyoensis, though not quite so pale, namely, in fresh plumage, cartridge buff. Tail (see figs. 2, 3) much shorter than in either gambeli or inyoensis; and bill averaging smaller than in any of the other three races.

Measurements.--Average of 14 males: Wing, 69.7 mm.; tail, 65.0; exposed culmen, 7.9; depth of bill at base, 3.8. For extremes, see accompanying table.

Range.--The higher mountains of central and northern California, southern Oregon (probably this subspecies), and northwestern Nevada. Occurs west in northern California through the Siskiyou and Salmon mountains and to South Yolla Bolly Mountain and Mount Sanhedrin; and south in the Sierra Nevada to the vicinity of Mount Whitney. Specimens examined, 182, from the following localities:

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Type locality.--Mount Wilson, 5500 feet altitude, San Gabriel Mountains, Los Angeles County, California. Type in coll. J. Grinnell.

Diagnosis.--Tone of coloration on sides, flanks and back distinctly plumbeous--more exactly, on sides and flanks the "smoke gray" of Ridgway (1912, pl. 46), and on back near the "mouse gray" of the same authority (pl. 51). The tail in this race is short as in abbrevialus, but the bill is long and heavy, averaging thicker through than in any of the other three races.

Measurements.--Average of 14 males: Wing, 70.0 mm.; tail, 65.4; exposed culmen, 8.5; depth of bill at base, 4.1. For extremes, see accompanying table.

Range.--Higher mountains of southern California, from the extreme southern Sierra Nevada in Tulare County, and the Santa Lucia Mountains in Monterey County, south to the Cuyamaca Mountains, San Diego County; also (probably this subspecies) in the San Pedro Martir Mountains, in northern Lower California. Specimens examined, 160, from the following localities, all in California:

General remarks.--In making use of the intrinsic color characters, which are important here in distinguishing subspecies, it is, of course, essential that the effects of extraneous factors be taken into account. Prolonged wear and fading evidently serve to weaken the intensity of the color tones, more especially the buffy ones. Then, too, chickadees seem peculiarly susceptible to discoloration by smoke, soot and charred wood; for example, our series from Cisco and Blue Cañon, stations along the Central Pacific Railway over the Sierra Nevada, even though taken in September and October almost immediately after completion of the fall molt, are obviously more or less begrimed with soot. On the other hand, the autumn- and winter-taken series from the Yosemite region and from the Siskiyou Mountains are clean, and show their intrinsic color tones to good advantage.

Intergradation undoubtedly connects the four races of the Mountain Chickadee into a continuous series of forms. Abundant material at hand from that portion of the Sierra Nevada immediately south of Mount Whitney shows complete transition from Penthestes gambeli baileyae to P. g. abbreviatus; in fact, many of the specimens can only be placed arbitrarily in one category or the other. Several examples from the vicinity of Mono Lake, in Mono County, California, and from along the west flank of the Sierras in Inyo County, insensibly bridge the interval between P. g. abbreviatus and P. g. inyoensis, especially when considered in connection with the individual variation to which each race is subject in about normal degree.

Material at hand from different parts of the Great Basin is unsatisfactory either in that it is scanty or because of the worn state of the plumage. A summer-taken series of 13 Mountain Chickadees (nos. 8952-8964, Mus. Vert. Zool.) from the Pine Forest Mountains, Humboldt County, Nevada, shows in color no approach to P. gambeli gambeli. In this respect it is like P. g. inyoensis, but the tail averages nearly as short as in P. g. abbreviatus. Taking all features into [513] account it seems best placed under abbreviatus. Fresh-plumaged fall specimens from this locality would make determination more certain.

A specimen (♂, no. 547, Mus. Vert. Zool.) from Anthony, Baker County, Oregon, taken October 16, 1907, might be referred to P. g. abbreviatus; but the tone of color of back and sides is much darker than usual in that form. It is certainly much darker than in P. g. inyoensis. Its tail is but 65.3 mm. long. A skin (♀, no. 18, Morcom coll.) from Camp Harney, Harney County, Oregon, February 17, 1875, has a tail length of 67.7 mm., and in depth of color is about intermediate between abbreviatus and P. g. gambeli. A specimen (♀, no. 136639, U. S. Nat. Mus., Biol. Surv. coll.) from Fort Spokane, Lincoln County, Washington, September 28, 1890, is almost identical with gambeli in coloration; but it, too, has a short tail, only 64.4 mm. long, though there is chance of error here, as several of the rectrices are missing. The writer prefers to leave these last three examples for the time being unplaced.

It is clear that intergradation between Penthestes gambeli gambeli and any one of the other three subspecies is less well established than between any two of these other three. But sufficiency of material from the proper localities through eastern Oregon and eastern Washington would likely prove its existence as is the case between the California forms.

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LITERATURE CITED

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